Photonics Dictionary

The material that produces stimulated emission from within a laser oscillator. Laser gain media may vary from extended-length glass fibers to submicron-length semiconductor material.

The lowest excitation power level at which a laser's output is mainly the result of stimulated emission rather than spontaneous emission.

Latency is the time interval between the stimulation or input of a system and the response or output. It is a measure of the time delay experienced in a system, network, or process. Latency can occur...

The pattern of physical or chemical changes that has taken place in a photographic emulsion, by its exposure to light, that will form a visible image when the emulsion is developed. Also known as...

Lens aberration resulting in image size variation as a function of wavelength. See also chromatic aberration.

A set of photodiodes with no gaps between them that can sense the displacement of a spot of light anywhere on the sensing area.

A method of measuring microbending losses in optical fiber by sandwiching a length of fiber between two parallel plates, with 150-grit sandpaper on the bottom plate. Different weights are placed on...

In a diode laser, a mode in the plane of the active layer that is perpendicular to the direction of the emitted beam.

A power loss caused by transverse or lateral deviation from optimum alignment of source to optical waveguide, waveguide to waveguide, or waveguide to detector.

A lateral shearing interferometer is an optical device used in interferometry to measure phase differences between two beams of light. Interferometry is a technique that combines and analyzes...

The perception of visual stimuli at the left and right outer boundaries of the visual field.

Light generated along the interface when light is incident in the neighborhood of the total internal reflection angle.

In photonics, a lattice refers to a periodic arrangement of optical elements or structures, often on a microscopic or nanoscopic scale. These optical lattices can be created using various techniques...

With respect to the crystal, the decrease in energy that follows the process whereby the ions, separated from each other by an infinite distance, are brought to their locations in the stable lattice....

The photographic record of the diffracted beams formed when heterogeneous x-rays emerging from a pinhole or slit impinge upon one crystal.

The angle between the light input propagation vector and the optical axis of an optical fiber or fiber bundle.

The numerical aperture of an optical system used to couple (launch) power into an optical waveguide.

A fiber used in conjunction with a source to excite the modes of another fiber in a particular fashion.

A Laurent polarimeter is an instrument used in optics for measuring the rotation of plane-polarized light caused by optically active substances. Optical rotation, also known as optical activity, is a...

The law stating that when light strikes a surface at such an angle that the reflected and refracted rays are perpendicular to each other, the maximum polarization of the light occurs in both...

The law stating that the angle of reflection is equal to the angle of incidence, the incident ray, reflected ray and normal to the surface, all being located in the same plane.

In physics, the law of reversibility is often associated with the concept of reversibility in thermodynamics. The law asserts that any process that occurs in a closed system can, in theory, be...

Defines the minimum operational standards for a self-sustaining fusion reactor as equivalence between energy released per volume unit and kinetic energy per unit volume.

In a fiber optic cable, the longitudinal length required for the transmission media, wrapped around a central member, to complete one helical wrap. Also called pitch.

In the optical shop, the process of positioning and marking a blank or lens before surfacing, cutting and edging.

The process of removing some of the constituents of a glass surface by chemical action.

A thin-film photoconductive cell that is sensitive to the infrared region. The photosensitive material of the cell is composed of lead selenide, and the cell is used in the detection of infrared...

A photoconductive cell having greatest sensitivity in the infrared region. The photosensitive material of the cell is lead sulfide, which is deposited on a glass plate.

A ferroelectric polycrystalline ceramic material used in optical memories for computers and as a piezoelectric transducer.

In a sequence of laser pulse emissions, the intitial pulse that often helps initiate a reaction at the target surface, whereas the trailing edge maintains the reaction.

In an optical waveguide, a mode whose field decays monotonically for a finite distance in the transverse direction but which becomes oscillatory everywhere beyond that finite distance.

In an optical waveguide, a ray for which geometric optics would predict total internal reflection at the core boundary, but which suffers loss by virtue of the curved core boundary.

The circle of confusion is a defocused or aberrated image of a point. Focus is generally set where the diameter of this circle is minimized or least.